A French minister has resigned from Nicolas Sarkozy's government after he was put under investigation for allegedly sexually assaulting two women who worked for him.

The departure of the civil service minister, Georges Tron – who denies the allegations – was announced by the prime minister, François Fillon, on Sunday.

French prosecutors were in the preliminary stages of investigating accusations of sexual aggression and rape against Tron, whose lawyer, Olivier Schnerb, said were "pure defamation" and "balderdash".

The investigation comes two weeks after the arrest of the former IMF head and Socialist presidential hopeful, Dominique Strauss-Kahn, who is facing sexual assault charges in New York.

Tron's position became untenable after the foreign minister, Alain Juppé, told a television show that although his colleague was "presumed innocent", he should consider resigning because "government ministers had to be above all suspicion."

The two women, aged 34 and 36, have lodged complaints with the public prosecutor, claiming Tron assaulted them between 2007 and 2010 while they worked at the town hall in Draveil, south of Paris, where he is the mayor.

The women claim the assaults started after Tron, who says he is a qualified reflexologist, offered to give the women foot massages. They say it was the arrest of Strauss-Kahn that encouraged them to come forward. "When I see that a little chambermaid is capable of taking on Dominique Strauss-Kahn, I told myself I did not have the right to stay silent," one of them told a French newspaper.

"Other women have perhaps suffered what I have suffered. I have to help them. We have to smash this omerta."

The Strauss-Kahn affair has triggered soul-searching in France about sex and power. After the shock and disbelief of the arrest of the man nicknamed the Great Seducer, French pundits have been questioning whether strict privacy laws and alleged media complicity have enabled politicians and celebrities to get away with unacceptable behaviour. Sunday's edition of the Journal du Dimanche wrote of a "before and an after DSK" (as Strauss-Kahn is known in France).

Strauss-Kahn had already been forced to apologise for a "lack of judgment" after an affair with a junior colleague at the IMF shortly after he took up his post in 2007.

Tristane Banon, a journalist, claimed in 2007 that Strauss-Kahn sexually assaulted her in 2002, but her claims were largely ignored by the mainstream French press and her mother, a Socialist politician and friend of the Strauss-Kahn family persuaded her not to go to the police.

Last week a women's association said one of the women, claiming she had been attacked by Tron, had come forward in November with a "credible" complaint against the 53-year-old minister.

In a statement, the European Association Against Violence Against Women at Work said: "Her credibility is not in question from our point of view."

Tron claims the women have a vendetta against him after being sacked from their jobs. "I am not naive – they are trying to echo an affair taking place the other side of the Atlantic," he told Reuters last week. In an interview prior to his resignation, he said: "The accusations against me are fantasy."